There is known in the prior art a control system for a gas-utilizing installation. Such a system is disclosed in Japan Patent No. 49-32004, 23 Mar. 1974. This system is characterized in that an installation for utilizing blast-furnace gas has a gas turbine placed in parallel with throttle valves, a valve controlling the delivery of gas to the gas turbine being opened or closed by remote control depending on the gas flow rate. The gas turbine load is determined by the extent of the opening of the control valve. The pressure of gas under the blast furnace top is automatically adjusted by a separate device for controlling the trottle valves.
When the quantity of the released gas drops because of a reduced load of the blast furnace, i.e. during a short-term changeover of the blast furnace to operation at a reduced gas pressure, a suitable pressure regulator develops a signal which is used to close the control valve at the inlet of the turbine.
Under normal operating conditions, the flow rate of blast-furnace gas exceeds the specified value and the pressure regulator produces a signal to fully open said control valve. The pressure of gas under the blast furnace top is regulated with the aid of the throttle valves. The shut-down of the turbine causes automatic closure of an emergency shut-off valve mounted at the inlet of the turbine and instant complete closure of the control valve. At the same time, the throttle valves are instantly opened.
This system is not connected automatically with the control system of the gas-utilizing installation, which makes it necessary to have special personnel to run it. It also does not exclude faults, which may cause serious damage to the equipment and create hazards to the personnel by exposing them to a toxic explosive furnace gas.
There is also known a control system, for an installation utilizing the energy of the pressure of outgoing blast-furnace gas, comprising a control diaphragm gate and a closing diaphragm gate, being both mounted on a gas turbine which is placed in parallel with a throttle unit of a blast furnace. The turbine is used to rotate an electric generator provided with a power-driven ventilator for its cooling. There is also provided an oiling system with an oil pump for both the turbine and the generator, as well as a system for regulating the rotational speed of the turbine rotor with a rotor-speed selector connected to said control and closing diaphragm gates. The control system also includes a device for converting input signals coming from a regulator of gas pressure under the blast-furnace top, which is connected to the inputs of said rotor-speed regulating system; a switch of said electric generator with a set of signalling and interlocking contacts used for connecting and disconnecting the generator to and from a power line; a device for synchronizing the rotor rotational frequency and the power-line frequency having first and second outputs connected, respectively, to an output of said electric generator and to an a.c. power line, the first output of the synchronizing device also being connected to said switch of the generator. The control system further includes a first sensor responsive to gas temperature at the inlet of the turbine placed in a furnace-gas conduit downstream of a gas heater introduced in the installation. The gas heater is provided with an ignitor means, and is connected with an input of a temperature regulator of a furnace gas passing to the turbine. A second sensor responsive to gas temperature is placed at the inlet of the gas turbine. Valves are provided with electric drives and are placed in conduits for the delivery and discharge of blast-furnace gas to and from the gas-utilizing installation, in conduits for the delivery of air and gaseous fuel to the gas heater, in a conduit for the delivery of inert gas to the installation, and in a conduit for the discharge of the contaminated inert gas from the installation (cf., for instance, the "Stal" magazine, No. 7, 1966, pp. 666-669).
This system provides for remote control of the valves in the conduits of the installation and also of the auxiliary devices of the gas turbine and generator during their start-up and shut-down operations. The control system includes automatic regulation, interlocking, and protection from an accidental drop of the furnace-gas pressure and an accidental rise of furnace gas temperature in excess of the specified limit. The system also provides for automatic shut-off of the air delivered to the gas heater upon a drop in the furnace-gas pressure.
The aforesaid system is not connected with the control system of the installation used during start-up, shut-down and changeover of the blast furnace to an operation with reduced gas pressure. During those transitional operating conditions the system requires the attendance of an operator and does not prevent a possible faulty sequence of operations, which may result of the grave consequences described hereinbefore.